[bubbabrent]

I am happy to pose this question to professionals.  I saw a cable program on sugar.  I have done some research on the topic of "bleached" white sugar.  I am amazed at the diametrically opposing views on the web.  It expressly stated sugar is white naturally and not bleached.  This is not what I learned years ago.  So I set off to research it.  I am not a chemist but understand that for example salt is salt whether it is Kosher, sea, mined, or dead sea.  I understand too that sugar is sugar.  The basic chemical makeup is what it is.  My basic question is is SO₂ (sulfur dioxide) used in any part of the "cleaning" of the sugar?  And in your expert opinion can this chemical remain on the sugar crystal for consumer consumption at the table?  Less important but of interest is "turbinado" sugar cleaned with SO2, if in fact SO2 is ever used, in such a way.  You may email me at nprfan2002@yahoo.com if you like.  Thank You for your time.     

[ATMyller]

Brown sugar is brown because it has impurities like organic fibres, iron and potassium salts. White or refined sugar is not bleached but purified sucrose. Refined sugar can be made by dissolving raw sugar and purifying it with a phosphoric acid and by filtration through a bed of activated carbon.

[Arkcon]

Salt and sugar are white solids purified away from colored impurities by fractional crystallization, as was described above by OP and the response. 

SO2 is a common oxidizer that will decolorize impurities, it is commonly used to "bleach" flour.  Since flour is not soluble, not a single compound, and would lose useful properties if one tried to crystallize it from a water solution, SO2 is used.  The SO2 also kills pests, and changes the behavior of the flour in ways that are desirable.

You probably could decolorize a sucrose solution with SO2, but it seems impractical to me.  The colored impurities, molasses and such, would still be there.  I don't expect the colored impurities in rock salt would "bleach away" if exposed to SO2.

[dzoys]

just to go out on a limb- why do diet enthusiasts swear by brown sugar being healthier?

do the rxn's described here with purifying sugar allow phosphoric acid and/or carbon to remain in the final product?
if so, do humans have any reason to be concerned?